Method and apparatus for heat treating materials

ABSTRACT

ENT ATMOSPHERES OF DIFFERENT COMPOSITION AND/OR DIFFERENT THERMAL VALUES CAN BE MAINTAINED IN THE RESPECTIVE COMPARTMENTS FOR CONTACT WITH THE LAYER.   A TUNNEL FURNACE HAS AN ELONGATED FURNACE CHAMBER ALONG WHOSE BOTTOM A SUPPORT TRAVELS IN LONGITUDINAL DIRECTION. FROM THE ROOF TRANSVERSE PARTITIONS EXTEND DOWNWARDLY TOWARDS THE SUPPORT AND SUBDIVIDE THE SPACE ABOVE THE SAME INTO A PLURALITY OF INDIVIDUAL TREATING COMPARTMENTS. MATERIAL TO BE HEAT-TREATED IS DEPOSITED ON THE SUPPORT AS RELATIVELY THIN LAYER WHICH IS ADVANCED THROUGH THE CHAMBER SO THAT EACH INCREMENT OF THE LAYER BECOMES EXPOSED TO THE RESPECTIVE COMPARTMENT. THE COMPARTMENTS ARE PROVIDED WITH INLETS AND OUTLETS FOR GAS SO THAT DIFFER-

Sept. 25, 1973 H. VON HIPPEL 3,761,359

METHOD AND APPARATUS FOR HEAT-TREATING MATERIALS 5 Sheets-Sheet 1 FiledJuly 13, 1971 INVENTOR. HANS JOACHIA VOA HIPPEL Sept. 25, 1973 H. VONHlPPEL 3,761,359

METHOD AND APPARATUS FOR HEAT-TREATING MATERIALS Filed July 13, 1971 5Sheets-Sheet P,

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INVENTOR. HANS 404cm, vomnPPn BY MOM/i M paw Sept. 25, 1973 H. VONHIPPEL METHOD AND APPARATUS FOR HEAT-TREATING MATERIALS Filed July 13,19 7 l 5 Sheets-Sheet 4.

- INVENTOR. HAN; JOACHIM You HIF'PEL BY Muff M Sept. 25, 1973 H. VONHIPPEL METHOD AND APPARATUS FOR HEAT-TREATING MATERIALS 5 Sheets-Sheet 5Filed July 13, 1971 a F w W m H. $63 swsu m5 ks w w$ mi km @mw xgmfi $Qb36 W M f. v N I /4 J 1 H M M I A 1 V s H H QRNG m nmq 4 igs mum M A N mwt United States Patent O METHOD AND APPARATUS FOR HEAT- TREATINGMATERIALS Hansjoachim von Hippel, 7771 Oberstenweiler,

Germany Filed July 13, 1971, Ser. No. 162,033 Claims priority,application Germany, Nov. 23, 1970, P 20 57 493.0 Int. Cl. Cb 49/06 US.Cl. 201-3Z 21 Claims ABSTRACT OF THE DISCLOSURE A tunnel furnace has anelongated furnace chamber along whose bottom a support travels inlongitudinal direction. From the roof transverse partitions extenddownwardly towards the support and subdivide the space above the sameinto a plurality of individual treating compartments. Material to beheat-treated is deposited on the sup port as a relatively thin layerwhich is advanced through the chamber so that each increment of thelayer becomes exposed to the respective compartment. The compartmentsare provided with inlets and outlets for gas so that differentatmospheres of different composition and/or different thermal values canbe maintained in the respective compartments for contact with the layer.

BACKGROUND OF THE INVENTION The present invention relates generally tothe heat treatment of materials, and more particularly to a novel methodand apparatus for effecting such heat treatment.

There is a world-wide continuous increase in the demand for gas as afuel, resulting not only from population increases and the greaterdemand occasioned thereby, but also from an increasing popularity of gasas a relatively clean and low-polluting fuel. Generally speaking, gasfor these purposes is available in two forms, either as so-callednatural gas or as so-called manufactured or industrial gas. Theavailability of natural gas is, however, strictly limited and only a fewcountries can draw on supplies of such natural gas. In consequence, theneed for manufactured or industrial gas is becoming greater.

However, the methods and apparatuses known heretofore for the productionof high-grade gas by the gasification of solid fuels have not beenentirely satisfactory. In fact, the methods known heretofore are stillrather inefiicient. When coal is to be gasified, the production of ahigh-grade gas in satisfactory volume necessitates completevolatilization and a complete and efficient suppression of theproduction of gases which are merely waste or ballast. Thus,volatilization must be exclusively performed with the addition of steamor carbon dioxide, but the thermal balance of the known processes isnegative.

The known processes cannot be performed in, say, gas producers of forinstance the rotary-grate type without the addition of oxygen to thesteam, an expedient which is rather expensive. Furthermore, and quiteapart from the question of oxygen availability and expense, the knownprocesses are difficult to control because it is necessary at all coststo avoid overheating or undercooling. Even if oxygen is added to thesteam, irrespective of the additional expenses involved, the addition ofoxygen will tend to change the composition of the gas in favor of carbon3,761,359 Patented Sept. 25, 1973 dioxide, that is creating theadmixture with the high-grade gas of an undesirable ballast gas. Also,to bring about complete volatilization and avoid the production ofballast gas, the prior-art processes must be continuously observed,monitored and controlled throughout the period of gas evolution. This,incidentally, is also true if the prior-art process is analogously usedfor reduction and smelting.

SUMMARY OF THE INVENTION It is, accordingly, an object of the presentinvention to avoid the disadvantages of the prior art.

More particularly it is an object of the present invention to provide animproved method of the type and for the purposes discussed above, and animproved apparatus for carrying out the method.

In pursuance of the above objects, and of others which will becomeapparent hereafter, one feature of the invention resides in a method ofthe type under discussion, particularly suitable for the gasifying orcoking of solid fuels or of oleiferous sands or for the smelting ofores. This method comprises, briefly stated, the provision of a tunnelfurnace having an elongated furnace chamber which is formed with alongitudinally travelling support, has a roof upwardly spaced from thissupport, and is provided with partitions which extend downwardly fromthe roof and subdivide the space above the support into a plural-- ityof individual treating compartments. The material to be treated isdeposited on the support in the form of a wide relatively thin layerwhich is advanced on and With the support through the chamber so thatsuccessive longitudinal increments of the layer become successivelyexposed to each of the compartments. In the respective compartmentsdifferent atmospheres and temperatures are established to which each ofthe aforementioned longitudinal increments becomes exposed.

According to the invention each of the compartments is provided withinlet or outlet openings for gases, which are preferably so disposedthat the inlet and outlet openings are located in alternate compartmentsso that gases of different compositions, different enthalpy anddifferent temperatures can be separately introduced or abstracted fromthe respective compartments. The volumes of gas, which are large inrelation to the bulk of solid fuel which can be volatilized, are incontact with the solid fuel for only brief periods of time. In thenormal gas generation process, carbon dioxide is first formed and onlysubsequently reduced in the cooler zones to monoxide, with the resultthat in the methods utilized heretofore any gas produced inevitablycontains a significant quantity of carbon dioxide which constitutes mereballast, that is which is useless for the intended purposes.

By contrast, the method according to the present invention makes itpossible to control the temperature from compartment to compartment byheating the partitions, by introducing specially selected gases such assuperheated steam or combustible hydrogen-containing gases, and by thusoptimizing the volatilization processes. Owing to the disposition of gasoutlets in the separate compartments the quality of gas produced in therespective compartments can be individually and immediately monitored.During coking, that is during the gasification of coke, large volumes ofgas evolve and the invention proposes to perform the process in aplurality of steps each of which involves one or more chambers and ineach of which only a fraction of the total quantity of gas is liberated.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments of the invention when read in connection with theaccompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal sectionthrough an apparatus for carrying out the present invention, withportions omitted for the sake of clarity;

FIG. 2 is a cross-section in vertical direction through the apparatusshown in FIG. 1;

FIG. 3 is a view similar to FIG. 2, but on an enlarged scale and of adifferent embodiment of the invention;

FIG. 4 is a diagrammatic fragmentary vertical longitudinal sectionthrough an apparatus according to the invention; and

FIG. 5 is a view analogous to FIG. 4 but illustrating the gas how inoperation of the apparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Discussing firstly theembodiment illustrated in FIGS. 1 and 2 it will be seen that referencenumeral 1 identifies rails on which a support for material to be treatedtravels through the diagrammatically illustrated furnace chamber of anon-illustrated tunnel furnace. The support is here in form of aplurality of closely adjacent coupled carriages which carry respectiverefractory pallets having upper exposed surfaces 2.

Deposited on the pallet surfaces 2 is a dual-layer bed of volatilizablematerial, namely a layer of coarse-grained material 7 and beneath it alayer of fine-grained material 8. The pallets 10 are provided withpreferably transversely extending conduits 9 which-at points along thelength of the furnace chamber at which it is desired to heat the pallets10move into registry with lateral burner heads 14 and exhaust gaschambers 15 so that the pallets can be heated sectionally in accordancewith given requirements.

The chamber also has a roof formed by bricks which are suspended fromgirders 12 and are identified with reference numeral 16. Additionallythere are provided partitionswhich may also be in form ofbricksidentitied with reference numeral 3 and projecting downwardly fromthe roof of the chamber towards but short of the pallet surfaces 2. Thissubdivides the space between the pallet surfaces 2 and the roof definedand composed of the bricks 16 into a plurality of working compartmentsor treating compartments 6. Preferably the partitions 3 can be adjustedin their elevation (not shown in FIG. 1) so that they can be raised andlowered with respect to the pallet surfaces 2. This makes it possible tohave their lower edges approach the surfaces 2 sufficiently to providean adequately tight seal between neighboring ones of the compartments 6so that different phases of the process can be performed in eachchamber, with one chamber containing for instance a reducing atmosphereand the adjacent one an oxidizing atmosphere.

As the drawing shows, especially in FIG. 1, the partitions 3 are alsoprovided with internal conduits 11 and can be heated by the admissionthereinto of combustion gases from burners 17 (see FIG. 2). Thus, heatrequired for performing any particular phase of the process can besupplied via the partitions 3. Gas inlet or burner openings 4 and gasoutlet openings 5 are provided in the roof bricks 16, and gas admittedat the openings 4 is forced downwardly into contact with the surface ofthe bed 7, 8 by the presence of the partitions 3.

FIG. 4 shows, incidentally, that the compartments 6 may be of differentwidth and it will be understood that they can be heated by burnersdisposed in side walls 19 or in the roof 18 as may be desired orreruired (see FIG. 4). Heating may be effected alternately from oppositesides, with the combustion gases leaving through openings 20 and beingfed in conventional manner to a recuperator.

If the method and apparatus are utilized not for volatilizing solidfuels but instead for smelting ores, for instance for making steel, apossibility which will be discussed in more detail later, the pallets 10will be configurated as troughs, tubs or the like 21 mounted on thecarriages as shown, with the carriages and troughs 21 forming an endlesschain or train. This is also more clearly shown in FIG. 4.

For the recovery of waste heat in the production of coke the roof abovethe coke 23 is equipped with a conduit or tube system 24 forming part ofa steam or hot water system 28. The conduits 9 may also be used asrecuperating channels for heating wind blown therethrough. Referencenumeral 25 in FIG. 4 shows a supply hopper from which for instance thefine-grained material for the layer 8 may be supplied, and referencenumeral 26 shows a supply hopper from which the coarse-grain materialfor the layer 7 may be supplied. Reference numeral 27 is utilized forillustrating diagrammatically in FIG. 4 the returning part or run of thetrain or chain of cars with their pallets or troughs.

The raising and lowering of the partitions is more clearly ilustrated inFIG. 3, where the partitions are identified with reference numeral 3'and where each of them is shown to be associated with a hydrauliccylinder 31, a piston 30 and a piston rod 29 Which connects therespective piston with the associated partition 3'. It is advantageous,according to an embodiment of the invention, to generate hightemperatures by means of electric arc heating. As shown in theembodiment of FIG. 3 this can be effected in a simple manner byconstructing some or all of the partitions 3 as arc heating electrodeswhich are preferably so arranged that a second or counterele'ctrode islocated a short distance downwardly of the arc heating electrode, withelectric current flowing from the arc heating electrode into the bed ofmaterial to be heated (which is rendered electrically conductive by thepresence of the coke) and entering from there into thecounter-electrode.

FIG. 5 shows the gas flow in an apparatus according to the invention,for instance as shown in FIG. 4, and the legends applied to FIG. 5, inconjunction with the arrows indicating gas flow and the indicatedthermal value in degrees Centigrade, are self-explanatory.

The heating of the partitions, as discussed above, permitsvolatilization to be performed with pure steam or carbon dioxide, orwith a mixture thereof, because the missing process heat can be suppliedvia the heated partitions.

According to the invention the proportion of the total gas volume neededfor volatilization is always introduced into one chamber in superheatedstate, and exhausted from a neighboring chamber or chambers, with thegas thus being forced to flow from chamber to chamber, and each timebeing forced downwardly into contact with the surface of the bed ofmaterial, as indicated by the brokenline arrows in FIG. 1. As a result,and this refers of course to coking or gasification of solid fuels, agas having a high hydrogen and carbon monoxide content and a minimumcontent of carbon dioxide is obtained because the flowing gas isrepeatedly contacted with the bed of coke at high temperature.

This high-calorie gas contains up to 45% of hydrogen, 45% of carbonmonoxide and just about 10% of heavier hydrocarbons. The reason for thisrelatively high content of heavier hydrocarbons is the fact that thegasification process according to the present invention can be performedin the presence of steam or of hydrogen-containing gases, which makes itpossible to achieve a higher yield of the heavier hydrocarbons thancould be achieved before. Moreover, the sulfur content can be reduced ifvolatilization is performed in an atmosphere which contains no oxygen,and if lime is added the retention of sulfur in the ash is furtherfacilitated.

Gas having the lowest heating value (as compared to quantities of gashaving higher heating values) is obtained at the end of thevolatilization of gasification process, and this gas is advantageouslyused for supplying the amount of heat missing for carrying out theprocess. About one third of the heat content of the fuel that isvolatilized is just used for maintaining the process, but the heat soused is theoretically recovered in the gas which is produced.

To prevent any part of the fuel during execution of the process frombecoming entrained by the gas stream which moves in contact with thefuel bed, the invention proposes to deposit the fuel on the support inthe earlierdcscribed two separate layers, namely with the finer grainforming a lower layer which is covered by the upper layer of coarsergrain, it being evident that the coarser grain 'will resist entrainmentmore than the finer grain could do.

Furthermore, it is also possible and intended according to one conceptof the invention to mix the feed (that is the incoming material which isbeing deposited on the support) with one or more binding agents of atype capable of preventing the evolution of dust and entrainment of fineparticles. Such binding agents may be tar or tar oils and/or lime ormilk of lime, or any combination of these.

As already briefly indicated before, the present method and theapparatus according to the present invention are suitable not only forgasifying or coking of solid fuels or of oleiferous sands or the like,but can also be employed for smelting of ores. When this latter type ofoperation is to be carried out, the ore is admixed with a solid orliquid fuel and conveyed on the support successively through agasification zone, a coking zone, a reducing zone and a melting-downzone. In the gasification and coking zones the fuel admixed with the oreis exposed to hot reducing gases or to superheated steam introduced intothe various compartments which make up the respective zones. Into thezone for reducing the ore an oxygencontaining gas is introduced in orderto support the combustion of surplus coke. However, this latter gas canalso be omitted. The meltingdown zone, mentioned above and alreadydescribed with respect to FIG. 4 for example, may be fitted with gasburners which may be supplied with the high-calorific combustible gaswhich is obtained in the gasification zone during operation of theprocess and apparatus.

Particularly when the smelting of ore is concerned, the support may becomposed of a plurality of carriages or the like which carry not theelements shown in FIG. 1, but carry upwardly open troughs or the likewhich latter may themselves be so designed that they can be heated(compare for example FIG. 5). Thus, these troughs 21 (FIG. 4) may beprovided with heating channels having open ends which move into registryduring advancement of the support, with laterally located stationarygas-supplying and gas-venting conduits or openings, as already describedearlier. The individual troughs will eventually be filled with moltenpig iron or steel and can later be tipped into a mixer at the pointwhere the support which in this case is at least composed of acontinuous chain of such carriages and troughsmoves from its working runinto its return run.

It will be appreciated that with such an arrangement installations ofextremely high performance characteristics can be provided. Forinstance, if an apparatus according to the present invention utilizes asthe travelling support a train of travelling pallets four meters wideand moving at a rate of speed of 0.1 meter/second, a daily capacity ofup to 5,000 tons of coal or output of coke, or of 10,000 tons of steelcan be achieved in a completely continuous process free of dustevolution. If the invention is employed in the production of coke and ofcourse the concomitant production of gas, there is the advantage overthe presently existing (but still experimental) coking processes that nospecial heat carrier material such as sand is required, and that thecoal to be gasified and coked need not first be briquetted orpelletized. If the invention is used for making steel, and thus forsmelting ores and converting the metal obtained into steel, an advantageobtained is that the liquid pig iron in the individual troughs whichtogether make up the travelling support can be selectively treated. Bythis it is meant that for instance decarburization and the addition ofalloying metals can be individually controlled as each trough moves intoand out of registry with the successive compartment. It should beremembered in this connection that in a modern high-performance blastfurnace the hot air must penetrate up to six meters into the ore andcoke mixture in order to reach the ore at the furnace center. Keepingthis in mind it will be readily understood that the present inventionwhich is performed on a travel ling bed will necessarily be far moreefiicient because it avoids the penetration requirement of the priorart. Additionally, because volatilization and coking of the fuelsurrounding the ore causes a carbon envelope to form around each grainof ore, the latter is always in direct and intimate contact with thecarbon needed for reduction purposes, unlike in a blast furnace wherethe ore is usually reduced by carbon monoxide at lower temperature.

Still speaking with respect to the smelting of ore, it is pointed outthat when the process has progressed to the coking stage, the quantityof heat needed for reduction purposes can be produced by blowing air oroxygen into the respective chambers involved, and the ore reduced by theenveloping carbon without being exposed to the oxygen. In thisutilization of the present invention it is particularly advantageous ifthe partitions can be raised and lowered as discussed earlier, to makeit possible to cleanly separate the several phases of the smeltingprocess from one another. Since the lime required for the slag hasalready been added during the preparation of the ore and is thereforealready contained in the carbon or coke enveloping the ore grains, theslag binding the sulfur is molten at the same time as reduction takesplace, and the molten iron fills the troughs of the travelling supporttrain. Because the iron is no longer in contact with coke it can bedirectly recovered as steel if the process is properly controlled.

From all of the foregoing it will be understood that the method andapparatus according to the present invention offer significantadvantages over what is known. Broadly speaking, these advantages can besummarized in three categories, namely firstly a complete volatilizationof fuels for the production of a high-calorific gas, secondly acontinuous process of coking with the recovery of the coking heat, andthirdly a process of smelting iron and non-ferrous ores which in thesmelting of iron permits the pig iron phase to be eliminated and itscost saved by a special control of the smelting process as pointed outabove.

If the feed, that is the incoming material which is to be processed, isprepared with tar or oils, for instance such as are obtained in coking,the evolution of dust will also be either substantially reduced orcompletely suppressed. Moreover, the process according to the presentinvention can be readily observed in every phase and each stage can becontrolled because of the division of the furnace into a plurality ofindividual Working compartments. The travelling support may also beconstituted by a suitable turntable (known per se) which aifords thedesired features. Of course, the configuration of the furnace chamhermust then be appropriately changed to accommodate it to that of theturntable.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofapplications differing from the types described above.

While the invention has been illustrated and described as embodied in anapparatus for the heat treatment of certain materials, it is notintended to be limited to the details shown, since various modificationsand structural changes may be made without departing in any way from thespirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be protected by Letters Patent isset forth in the appended claims:

1. A method of the character described, particularly for gasifying orcoking solid fuels or oleiferous sands or for smelting ores, comprisingthe steps of providing a tunnel furnace having an elongated furnacechamber formed with a longitudinally travelling support, a roof upwardlyspaced from said support, and partitions at least some of which arehollow extending downwardly from said roof and subdividing the spaceabove said support into a plurality of individual treating compartments;depositing a material to be treated on said support in form of a widebut relatively thin layer; advancing said layer on said support throughsaid chamber so that successive longitudinal increments of said layerbecome successively exposed to each of said compartments; establishingin the respective compartments different atmospheres and temperatures towhich each of said longitudinal increments become exposed; andcirculating hot gas through at least some of said hollow partitions.

2. A method as defined in claim 1, wherein the advancing layer yieldsinto the respective compartments liberated gases which have differentcalorific and compositional parameters; and further comprising the stepof abstracting said gases from said chambers separated according to atleast one of said parameters.

3. A method as defined in claim 2; further comprising admittingextraneous gases to said layer for assisting volatilization; and whereinthe step of abstracting said liberated gases comprises simultaneouslywithdrawing said extraneous gases.

4. A method as defined in claim 1; further comprising the steps ofadmitting streams of superheated volatilizing gas into alternate ones ofsaid compartments for contact with said layer and passage beyond therespective partition into an adjacent compartment; and withdrawing suchgas from the respectively adjacent compartment.

5. A method as defined in claim 1, wherein said material is a solid fuelto be coked; and further comprising the steps of admitting flue gasesinto contact with said material during coking thereof for coolingpurposes; and utilizing the weak gas produced for heating respectivecoking zones of said chamber.

6. A method as defined in claim 1, wherein said material is a solid fuelto be coked, and wherein said chamber has a bottom wall provided withchannels which communicate with said chamber; and further comprising thestep of blowing cold air through said channels with the latterfunctioning as recuperators.

7. A method as defined in claim 1, wherein said material is a solid fuelto be coked, and wherein said chamber comprises conduits provided insaid roof; and further comprising the step of cooling said material bypassing a cooling medium through said conduits.

8. Amethod as defined in claim 1, wherein said material is an ore;further comprising the steps of admixing said ore with a combustiblefuel prior to advancement of said layer through said chamber; andconducting the thus-obtained mixture successively through avolatilization and coking zone for the fuel and thereupon through areducing zone for the ore, all of said zones being defined by saidcompartments.

9. A method as defined in claim 8; and further comprising the step ofadvancing said ore from said reducing zone directly into a melting zone.

10. A method as defined in claim 8, wherein the step of admixing saidore with said fuel comprises breaking the ore, providing groundadditives, and admixing said ore with said additives and fuel to form afiowable mass; and further comprising the step of depositing acontinuous at least substantially uniform layer of said mass on saidsupport.

11. A method as defined in claim 10, wherein said ore is broken to agrain size smaller than that of said additives.

12. An apparatus of the character described, particularly for gasifyingor coking solid fuels or oleiferous sands or for smelting ores,comprising a tunnel furnace having an elongated furnace chamber providedwith a floor and a roof; a travelling support in the region of saidfloor and adapted to travel longitudinally of said chamber; a pluralityof partitions extending from said roof downwardly towards said supportfor subdividing the space above the latter into a plurality ofindividual treating compartments, at least some of said partitions beinghollow; gas inlet and outlet openings arranged in alternate ones of saidcompartments so that gas admitted into one of said compartments mustpass beneath a respective partition into the adjacent compartment foraccess to the outlet opening herein; and means for circulating hot gasthrough. said hollow partitions.

13. An apparatus as defined in claim 12, wherein said partitions extendtransversely of the direction of travel of said support.

14. An apparatus as defined in claim 12; and further comprising heatingmeans for heating said partitions.

15. An apparatus as defined in claim 12; and further comprising controlmeans for raising and lowering said partitions with reference to saidtravelling support.

16. An apparatus as defined in claim 12, wherein at least some of saidpartitions are constructed as arc-heating electrodes; and furthercomprising counter-electrodes for cooperation with and locateddownstream of the respective arc-heating electrodes, and a source ofelectric energy connectable with said electrodes.

17. An apparatus as defined in claim 1, wherein at least some of saidpartitions are constructed as arc-heating electrodes; and furthercomprising a source of electric energy connectable with said electrodes.

18. An apparatus as defined in claim 1, said support comprising acontinuous chain of individual but connected receptacles composed ofrefractory material.

19. An apparatus as defined in claim 1, wherein said support comprises aplurality of hollow components which are adapted to be heated.

20. An apparatus as defined in claim 1, said material comprising finerand coarser particles; and further comprising depositing means forseparately depositing first said finer and atop the same said coarseparticles on said support.

21. An apparatus as defined in claim 1, wherein said support comprises aturntable.

References Cited UNITED STATES PATENTS 1,814,463 7/1931 Trent 202-1173,464,892 9/1969 Bennett 202-98 (Other references on following page) 9UNITED STATES PATENTS 3/1934 Bunce et al. 202-117 5/1924 Lamie 202-1037/1971 Kemmerer 201-40 5/1933 Karrick 201-40 X 7/1940 Soubbotin et al.201-98 FOREIGN PATENTS 1916 Great Britain 201-19 1964 Germany 202-98 10540,021 1955 Belgium 202-98 NORMAN YUDKOFF, Primary Examiner D. EDWARDS,Assistant Examiner US. Cl. X.R.

